Merge lp://staging/~3v1n0/nux/x11-conffile-on-unity-only into lp://staging/nux/artful

Unmerged revisions

895. By Marco Trevisan (Treviño) on 2018-06-13

Revert: "debian: don't consider the Xsession.d script as a config file anymore"

It seems something there's not full agreement on it, so to avoid further discussions
I'm reverting this back. However I strongly believe that given the current tools we have
this is the way to go, as debian doesn't provide other tools to get this done.
Nor X11 can move files outside of /etc.

894. By Marco Trevisan (Treviño) on 2018-06-13

gtest: update default google-test prefix to match distro

893. By Marco Trevisan (Treviño) on 2018-06-13

debian: don't consider the Xsession.d script as a config file anymore

This is just a script to be loaded, and not something the user is supposed to change,
so it should be removed on simple package removal.
To achieve this, as per maintainer-guide 5.3, using sym-links is the standard way.

892. By Marco Trevisan (Treviño) on 2018-06-13

50_check_unity_support: only run when called from an unity session

The content of $XDG_CURRENT_DESKTOP is checked inside a sub-shell
not to affect the value of IFS for all the scripts sourced by the X session.

If running in Unity we should call unity_support_test, not inside gnome
ubuntu X sessions.

XDG_CURRENT_DESKTOP values are currently the followings:
 - unity before 17.10: Unity
 - unity after 17.10: Unity:Unity7:ubuntu
 - gnome session: GNOME
 - ubuntu gnome session: ubuntu:GNOME

891. By Marco Trevisan (Treviño) on 2018-06-12

50_check_unity_support: only export LIBGL_ALWAYS_SOFTWARE=1 on command failed